The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Examples of video data compression technologies include H.261, H.263, MPEG-2, and MPEG-4. According to the video compression technologies, encoding each image is carried out after dividing the same into fixedly sized macroblocks which are composed of rectangular 16×16 pixel areas of a luminance or luma component and rectangular 8×8 pixel areas of a chrominance or chroma component. All of the luma and chroma components of the respective macroblocks are spatially or temporally predicted, and the resultant predicted residuals are transformed, quantized, and entropy-coded prior to transmission.
A block mode used in an existing video encoding apparatus encodes a flag indicating that a current encoding target block uses a predicted motion vector and has no transform coefficient to be encoded, and does not encode any more information. In the case of a block that does not use a predicted motion vector or has a transform coefficient to be encoded, type information of the block and prediction information of the block (a difference vector from the predicted motion vector and a reference picture number) are encoded and a transform coefficient is encoded.
However, in such typical video compression technologies, it is difficult to efficiently encode a block that has only a difference motion vector as data to be encoded and has no transform coefficient to be encoded, or a block that has no difference motion vector and has only a transform coefficient to be encoded, and it is difficult to efficiently encode various information used to encode a video.
In addition, the operation in unison between encoding and decoding the video makes it difficult to expect a highly efficient video decoding from the already deteriorated compression efficiency of the video encoding.